In March 2021, the Company’s board of directors and stockholders adopted the 2021 Equity Incentive Plan (the “2021 Plan”), which became effective on March 25, 2021, the date of the underwriting agreement related to the Company’s IPO. Upon adoption of the 2021 Plan, the Company restricted future grants from its 2018 Plan.

Under the 2021 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units, performance stock awards, performance cash awards and other forms of stock awards to employees, directors and consultants, including employees and consultants of the Company’s affiliates. The number of shares of common stock available for issuance under the 2021 Plan will automatically increase on January 1 of each calendar year, starting on January 1, 2022 through January 1, 2031, in an amount equal to 5% of the total number of shares of the Company’s common stock on the last day of the calendar month before the date of each automatic increase, or a lesser number of shares determined by the Company’s board of directors. As of June 30, 2023, the total number of shares available for future issuance was 6,088,014.

The following table summarizes stock option activity for the six months ended June 30, 2023:


	Options			Weighted-Average Exercise Price
Outstanding as of December 31, 2022		5,396,719		$	11.64
Granted		2,764,064		$	7.76
Exercised		(7,796	)	$	0.56
Forfeited		(139,914	)	$	12.56
Balance at June 30, 2023		8,013,073		$	10.30

Stock-based compensation expense has been reported in the Company's condensed statements of operations as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
Research and development	$	1,619	$	1,212	$	3,101	$	2,248
General and administrative		2,100		1,405		4,044		2,729
Total	$	3,719	$	2,617	$	7,145	$	4,977

In March 2021, the Company’s board of directors and stockholders adopted the ESPP, which became effective on March 25, 2021, the date of the underwriting agreement related to the Company’s IPO. The ESPP permits eligible employees who elect to participate in an offering under the ESPP to have up to 15% of their eligible earnings withheld, subject to certain limitations, to purchase shares of common stock pursuant to the ESPP. The price of common stock purchased under the ESPP is equal to 85% of the lower of the fair market value of the common stock at the commencement date of each offering period or the relevant date of purchase.

The number of shares of common stock available for issuance under the ESPP will automatically increase on January 1 of each calendar year, starting on January 1, 2022 through January 1, 2031, in an amount equal to the lesser of (i) 1% of the total number of shares of the Company’s common stock on the last day of the calendar month before the date of each automatic increase and (ii) 1,200,000 shares; or a lesser number of shares determined by the Company’s board of directors. As of June 30, 2023, the Company had issued 82,437 shares of the Company's common stock under the ESPP and had 1,633,813 shares available for future issuance.